Tight gas formations, such as Khuff carbonate, pre-Khuff sandstone and shale gas formations with high compressive strength require hydraulic fracturing procedures in order to open the reservoir formation and enhance the flow of gas to the well bore for production. In such tight gas-containing reservoir formations, a perforating gun is used to initiate formation breakdown by detonating high-performance deep-penetrating shaped charges that maximize perforation length and entry hole size to start the hydraulic fracturing or “hydrofracking”, in order to enhance hydrocarbon production and optimize well flow.
The tubing-conveyed perforating (TCP) gun employs a drilling rig at the surface in operation to handle the tubing that conveys the gun to the desired depth in the well bore.
Perforating guns are available in various configurations. In each case, the key objective of the selection of the gun and the size, nature and set up of the shaped charges is to create a predetermined pattern of perforations over a predetermined wellbore interval.
Currently, stimulation of the reservoir is commenced after a single gun run to perforate the reservoir. The creation of deep perforations with large diameters has been a problem that has not been solved by the petroleum industry and there is a compromise between perforation diameter and penetration depth. To create deep perforations that bypass damaged zones, the perforation diameter should be small and the force of the shaped charge narrowly focused. Current perforation practices fail to provide deep penetration with large diameter penetration, especially in formations with high compressive strength, and also can fail to bypass formation damage.
The problem to be solved is how to provide a new method for initiating the hydraulic fracturing in tight gas reservoirs at a deeper point of penetration having a larger diameter than is currently possible in order to thereby improve well productivity and injectivity. Currently, the hydraulic fracturing of tight formations is initiated after only a single reservoir perforation. It would be desirable to provide a method and apparatus capable of completing a plurality of reservoir perforations or penetrations at the same position in order to produce a deeper penetration with a larger diameter before the hydraulic fracturing is commenced.
The problem can also be stated as how to position and maintain the TCP gun at the same location for successive or repeated reservoir penetration shots in wells operating with a rig, or perforating guns that are deployed by wireline and/or coiled tubing unit.
An associated problem is to provide a latching tool having the capability of unlatching with a downward force in addition to the current upward unlatching force.